A: Very little, says Keri. A white T-shirt has an SPF of only about 3, she says. But you can buy sun-protective swimwear, coverups, hats, even long-sleeve shirts and pants. The clothing is impregnated with zinc oxide or titanium oxide, the same ingredients in many sunscreens. While sunscreen is measured in SPF (sun protection factor), clothing is rated in UPF (ultraviolet protection factor). Try stores like Target, Kmart and Walmart or Google "sun protective clothing."
A: Dark-skinned people are less susceptible because the melanin that gives their skin its color absorbs UV radiation, Keri says, "but they can still burn."
Q: What about tanning lotions that bronze the skin?
A: They're OK, Keri says, as long as the active ingredient is dihydroxyacetone (or DHA), which reacts with dead cells on your skin to turn you tan. But the tan you get gives you protection up to only an SPF of 3, so it won't help much against the real sun. Some tanning creams include protective ingredients with SPFs of 15 or higher. But that lasts only about 90 minutes, not the duration of the tan, which is usually about five days.
Q: Can I get a safe tan at a tanning salon?
A: The Skin Cancer Foundation warns against them altogether. So does Keri: "They're just a way to try to convince consumers they're healthy when they're not," she says.
Q: I hear the human body needs vitamin D and gets it from unprotected exposure to the sun. Will I get enough if I take so many protective measures?
This is a matter of debate in the medical community. Some doctors, including rheumatologist James Dowd, author of the "The Vitamin D Cure," advise at least some unprotected exposure to the sun. The known benefits of vitamin D - which can be blocked by SPFs rated 8 or higher - include helping calcium build strong bones, and researchers have looked in the vitamin's role in staving off colon cancer, multiple sclerosis, diabetes and heart disease.
Dermatologists like Keri say the risks of damage from unprotected exposure outweigh the potential benefits, and that vitamin D can be obtained in foods and supplements. Good sources include salmon, mackerel, sardines, fortified milk or cereals like Kashi or Total.
The National Institutes of Health, pointing out that UV radiation is a carcinogen that accumulates over a lifetime, concludes: "It is not known whether a desirable level of regular sun exposure exists that imposes no (or minimal) risk of skin cancer over time."
There is no definitive answer, so you may want to consult your doctor.